Self-Sustaining Tunable Multi-Frequency Oscillators Using Atomically-Thin Semiconducting Multimode Resonators

从基础科学探索到通信和传感技术，机械振荡器在许多关键应用中都是必不可少的。虽然近几十年来器件的小型化已经创造了许多谐振微纳机电系统（MEMS和NEMS）作为制造振荡器和时钟的新频率参考，但通过在新的纳米结构中利用新兴谐振器来设计超低功耗、低噪声晶体振荡器仍然存在主要挑战。该项目旨在发现基于原子层二维（2D）半导体的多模谐振器实现的多频自维持振荡器的新科学和工程原理，重点关注以前未探索的效果和潜在的前所未有的功能和性能。2D NEMS基于机械活性原子薄半导体晶体，这些晶体来自“超越石墨烯”层状材料，提供了一系列有吸引力的机电属性。多模二维NEMS谐振器是一类新型的振动NEMS，具有丰富的多共振模式和有趣的可调谐特性。利用在射频（RF）和微波波段振动的多模二维NEMS谐振器的频率参考和选择性功能，自维持反馈振荡器与无源谐振器的不同之处在于，它们具有自己的稳定极限环，并且可以在没有外部周期性驱动的情况下维持周期性振荡。综合STEM教育计划的目标是通过以下方式教育和激励年轻人：(i)为K-12学生提供新的外展计划，以了解振荡并学习时钟和计时设备的迷人历史，（ii）在凯斯西储大学（CWRU）为高中生进行暑期研究，以及（iii）积极扩大代表性不足和经济弱势群体的参与，特别是通过将外展计划扩展到克利夫兰地区的公立学校。该项目的目标是证明二维半导体可以实现高度可调谐的自维持振荡器，发展二维NEMS振荡器工程和片上集成的原理，并探索二维平台中晶体振荡器的最终极限。本项目将建立二维晶体振荡器信号转导和反馈机制的基本原理，为设计适用于二维系统的超低功耗和调谐电路奠定基础，并解决小信号检测、寄生效应抑制、非线性、调谐和功率处理等关键挑战。它还将探索在射频和微波频率下二维晶体自维持振荡中的相位噪声。这项研究将通过创新的反馈电路设计实现，这将大大超越简单的维持放大器，足以满足单谐振器，单模反馈振荡器。该项目以电路器件协同设计为特色，目标是最终实现具有相位噪声工程的全新单片多模振荡器。该项目将创建和建立一个新的分支，二维晶体振荡器，在快速崛起和增长的二维器件和系统领域。这项研究将在器件物理和控制二维晶体振荡器的工程原理方面产生大量的新知识，从而拓宽了当前二维系统知识的视野。该发现还将导致在原子层中实现二维定时和频率控制功能的技术。这将有助于建立二维机电系统作为一个新的支柱，与基于原子层的电子学和光电子学并行，以支持未来的二维半导体范式。

Mechanical oscillators are essential and ubiquitous in many critical applications from fundamental science explorations to communication and sensing technologies. While miniaturization of devices in recent decades has created many resonant micro- and nanoelectromechanical systems (MEMS and NEMS) as new frequency references for making oscillators and clocks, major challenges remain in engineering ultralow-power, low-noise crystal oscillators by utilizing emerging resonators in new nanostructures. This project aims to discover new science and engineering principles in multi-frequency self-sustained oscillators enabled by multimode resonators based on atomic layer two-dimensional (2D) semiconductors, with a focus on previously unexplored effects and potentially unprecedented functions and performance. 2D NEMS are based on mechanically active atomically-thin semiconducting crystals derived from "beyond-graphene" layered materials that offer a spectrum of attractive electromechanical attributes. Multimode 2D NEMS resonators are a new class of vibrating NEMS with intriguing and tunable properties rich in their multiple resonance modes. With frequency reference and selectivity functions harnessed from multimode 2D NEMS resonators vibrating in radio-frequency (RF) and microwave bands, the self-sustaining feedback oscillators are distinct from passive resonators in that they possess their own stable limit cycles, and can sustain periodic oscillations without an external periodic drive. The goal of the integrated STEM educational plan is to educate and motivate youth by (i) a new outreach program for K-12 students to understand oscillations and learn the fascinating history of clocks and timing devices, (ii) summer research at Case Western Reserve University (CWRU) for high-school students, and (iii) actively broadening participations from underrepresented and economically disadvantaged groups, especially by extending outreach programs to public schools in Cleveland area. The objectives of this project are to demonstrate that 2D semiconductors can enable highly tunable self-sustaining oscillators, to develop the principles of 2D NEMS oscillator engineering and on-chip integration, and to explore pathways toward ultimate limits of crystal oscillators in the 2D platform. This project will establish the fundamental principles of signal transduction and feedback mechanisms in 2D crystal oscillators, lay the foundation for ultralow-power and tuning circuit design suitable for 2D systems, and address critical challenges in small-signal detection, parasitic effect suppression, nonlinearity, tuning and power handling. It will also explore phase noise in self-sustaining oscillations in 2D crystals at RF and microwave frequencies. The research will be enabled by innovative feedback circuit designs that will go significantly beyond the simple sustaining amplifiers that are sufficient for single-resonator, single-mode feedback oscillators. This project features a circuit-device co-design perspective, with the goal of eventually enabling entirely new, monolithic, multimode oscillators with phase noise engineering. This project will create and establish a new branch, 2D crystal oscillators, in the rapidly emerging and growing field of 2D devices and systems. The research will generate a plethora of new knowledge in both device physics and engineering principles that govern the 2D crystal oscillators, thus broadening the horizon of current knowledge of 2D systems. The findings shall also lead to enabling technologies for 2D timing and frequency control functions in atomic layers. This will contribute to establishing 2D electromechanical systems as a new pillar, in parallel to electronics and optoelectronics based on atomic layers, to support the future 2D semiconductor paradigm.